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This is TOTALLY incorrect.
you have to radius the inner bend on a 90 to have ANY effect on airflow. without it, turning vanes are still needed...

radiusing the outer bend only saves metal costs...

Seems to be a professional difference of opinion on this point.

I'm not an engineer but I think I have a basic understanding of fluid flow. If I were building the return drop in its present location, I would have made it the full 20X25 size of the filter box all the way up. and included turning vanes.

With the overall leakage of the panned joists, I'm not sure if this would just be perfuming the pig, though.

My question on aero sealing of return ducts is, how do you keep the material out of the blower? Do you have to disassemble the ducts enough so that you can use a different fan to depressurize the returns? Also, I presume, but don't know for sure, that there are aero sealants available that are green, meaning zero VOC for starters?

By the way, the supply ducts are plenty leaky too. At least they are sheet metal instead of ductboard stapled between joists--so I've been going around sealing everything that could be a leak, working my way out from the furnace (the point of highest pressure).

Earlier I mentioned I need manual J calculations to be run because I don't believe they ever were. What I meant to say was that I need manual J and manual D calculations. It looks wrong to me, for example, to have the same CFM supplied to an interior master bedroom closet as there is to an exterior 13X13 bedroom. Proof is in the pudding: the closets were three degrees above the zone setpoint and the bedroom was four degrees below--until I shut off the air to the closets, which increased the bedroom airflow from about 65 CFM to about 90.

This is not work that a professional who cares about his work, and his referrals, should force a homeowner to undertake. In my humble opinion.

New construction is very "cut throat" especially in a tract home situation. Every corner is cut to keep costs low because the builder tries to keep costs low, ductwork usually suffers to keep costs low as well as inexperienced installers to keep labor cost low. If it was a custom built home then the hvac sub should have met with you and the builder and given you options and gotten input from you about how important certain things such as IAQ, humidity etc is to you and your family. A good duct system installed per manual D would have balancing dampers at each branch line on the trunk line that would be balanced and set when installed to match the heat gain/loss calculated by manual J of the room.

This is TOTALLY incorrect.
you have to radius the inner bend on a 90 to have ANY effect on airflow. without it, turning vanes are still needed...

radiusing the outer bend only saves metal costs...

Maybe in a perfect world. I'm not saying this is correct or right, but (almost) no one in my area (of maybe 350,000 people) get a radius elbow. They're lucky if they get a
25"x 16" filter. Most will use the boughten 20"x 16" boot/drop. Turning vanes..........Right!! Not even on EAC do they use turning vanes.

Why do the geothermal systems ask for a radius heel, but not the throat.........just curious?

New construction is very "cut throat" especially in a tract home situation. Every corner is cut to keep costs low because the builder tries to keep costs low, ductwork usually suffers to keep costs low as well as inexperienced installers to keep labor cost low. If it was a custom built home then the hvac sub should have met with you and the builder and given you options and gotten input from you about how important certain things such as IAQ, humidity etc is to you and your family. A good duct system installed per manual D would have balancing dampers at each branch line on the trunk line that would be balanced and set when installed to match the heat gain/loss calculated by manual J of the room.

This is not a tract home, it's a close to seven-figure semi-custom.

I was required to work directly with the HVAC contractor, although he didn't work FOR me--he worked for the builder. In the end I could specify the equipment I wanted, for which, as I've said, I paid a massive markup. My other option was to take the standard package from the builder and rip it all out the day after settlement.

In hindsight, that would have been a better choice. The HVAC contractor (HAC contractor really, I don't think he knows a thing about ventilation) refused to do anything I wanted with the ductwork. To be perfectly honest, after my first meeting with him, I wanted someone else, but by then I was stuck by the terms of my contract.

This is all water under the bridge at this point. The question is where I go from here to get closer to having the system I wanted to begin with?

Clearly, replacement of all of the accessible panned joist ductboard with real sheet metal ducts is going to be required. Possible replacement of other incorrectly sized ductwork too, and probably the brand new XC16-048 as well. It's entirely possible that walls have to be pulled apart as well. Obviously, relocating the zone 2 thermostat to the master bedroom, where I requested it be installed in the first place too. (I only mention that because it would have taken 5 minutes during construction, and now it's going to be a pain in the rear end). These things may well have to be handled in phases as my family has to live here.

First steps for me are an energy audit and manual J, S, and D calculations. Hopefully that will tell me what the extent of the losses are, and how much of the ductwork has to be replace due to sizing issues. The return air drop (the subject of this conversation) will be replaced along in there somewhere.

Thanks for the thoughts. I appreciate any other comments or recommendations.

.........I know what you're thinking, what does some PE with a fancy calculator know about airflow in the real world.........

Originally Posted by homeownerjim

.......I'm not an engineer but I think I have a basic understanding of fluid flow........

I thought you were.

Wow, close to a million bucks and you have to put up with that kind of horse manure?

Other than the shooting, how was the play Mrs. Lincoln?

Just a couple of comments;

The floor boots looked pathetic.

To me the return air duct looks odd with the filter where it is and they should've made it larger.

Building cavities can be used for return chases if they are sealed properly but it's a last resort and not a best practice.

Contract or not, I would have been on that builders a$$ like stink on a fresh turd. Totally unacceptable.

If you can physically get to the ducts Aeroseal is a decent option.

The insulation on the suction line is primarily to prevent sweating but the installers attitude says all, especially in front of a homeowner. Complete lack of professionalism. I'd bet a dollar he was young.

Wireless thermostats are an option these days.

Good luck Jim, keep us posted.

The picture in my avatar is of the Houston Ship Channel and was taken from my backyard. I like to sit outside and slap mosquitos while watching countless supertankers, barges and cargo ships of every shape and size carry all sorts of deadly toxins to and fro. It's really beautiful at times.....just don't eat the three eyed fish....

Wow, close to a million bucks and you have to put up with that kind of horse manure?.

Before you all think I'm some kind of schnook, there was a lot that went right with this deal for me and my family. The HVAC system just wasn't one of those things. I was also very pressed for time during construction due to moving and so on; I just couldn't watch construction on a daily basis. The worst part, as I've already mentioned, was that the arrangement meant that the subs didn't directly answer to me. As I found out, in the end I simply couldn't just tell them to do something, or fire them. The HVAC installer I was forced to use wouldn't have gotten a foot on the property, if it had been up to me.

Originally Posted by Cooked

The floor boots looked pathetic.

Indeed. Fortunately those are easily accessible and easy enough to seal, if time-consuming.

Originally Posted by Cooked

To me the return air duct looks odd with the filter where it is and they should've made it larger.

Thanks, me too. We'll get that addressed, once I repair the return ducts sufficiently to ensure that most of the return air actually enters through the return registers.

Originally Posted by Cooked

The insulation on the suction line is primarily to prevent sweating but the installers attitude says all, especially in front of a homeowner. Complete lack of professionalism. I'd bet a dollar he was young.

No, he wasn't young. I should have been more specific: I'm talking about the suction line from the condenser to the house, not inside the house. This part of the line bakes in its southwest exposure. If this line is sweating (or even if it isn't) heat is transferring into the refrigerant, no? I thought leaving the job with a dollar's worth of insulation hanging off this pipe was "wall of shame" sloppy. Just my opinion.

Originally Posted by Cooked

Wireless thermostats are an option these days.

Speaking of sloppy, I can't get over mounting the zone 2 thermostat in the hallway. Apparently it was his effort to balance the temperature from one end of the house to the other: one end would be above the setpoint, the other below, maybe the homeowner won't notice. Just to add insult to injury, he mounted the thermostat so as to cover a 4 inch square hole in the sheetrock, leading to who knows where. I'm going to have to be in the attic anyway, so I'll pull the wire over to the master bedroom and get it properly located.

I want to thank everyone who's replied on this thread. Just putting my issues down in writing has actually helped.

I'm focused on fixing the system so it works the way I wanted from the start.

To begin with, I'll get a PE to do the manual J, S, and D calculations and a duct test to see exactly how bad the leakage is. Then I'll see what can be reasonably done to improve the situation. There are a lot of panned joists in the basement, for example, that are still accessible for replacement, before I start ripping open walls.

Somewhere along the way I'll address the ventilation issue also. Unfortunately I probably won't get the HRV I wanted with its own supply and return ducting, but we'll do something to ensure adequate air changes and control where the fresh air is coming in.

I hired a P.E. who does not do HVAC work to evaluate the condition of the ducts. Bottom line is that the ductwork in this new house is worse than I thought. There is gross duct leakage into unconditioned space on the order of 300-400 CFM at a fairly low pressure differential. Clearly there's either a one big hole or a whole bunch of small ones.

The likeliest spot is the attic. I suspect that they cut a hole in the supply trunk, didn't use it for some reason, and then just wrapped insulation over it. I won't even bore you with my disgust. Clearly doesn't come anywhere close to meeting code which means no duct test was done, or the inspector was asleep, or both.

So I'll be looking for someone who can do quality retrofit work to crawl around up there. There's related work in the attic as the ductwork for four bath fans needs to be replaced with insulated and supported ductwork, and wires need to be pulled to relocate the thermostat to the master bedroom where it belonged in the first place. I'll also probably want to relocate a bathroom supply register somewhere other than directly over the bathtub. Don't get me started on that piece of foolishness.

Probably I'll try to find someone on a time and materials basis because no one can predict what we'll actually find up there. And have the engineer back on-site before wrapping up to confirm the leaks have all been found and fixed. Just need to find a detail oriented person or company that doesn't mind cleaning up someone else's mess. Once this is done, I can get to replacing the A/C condenser and coil and adding the ERV, but no point till the ducts are tight.

Appreciate the comments. Again, this is on a house that was new in August 2012. This is beyond a mistake or oversight--this leak is of the magnitude that someone obviously knew about it and just couldn't bring himself to care.